media-sound/cadence installs the file /etc/X11/xinit/xinitrc.d/61cadence-session-inject that sets audio plugin path variables (LV2_PATH, VST_PATH...) to /usr/lib/ (e.g. /usr/lib/lv2) instead of /usr/lib64 by default. As a result, software that depends on media-libs/lilv (and probably other sound plugin users) can't find plugins installed in the system (e.g. lsp-plugins). This is especially problematic with easyeffects, because it doesn't provide a way to set more audio plugin search paths.
The issue can be easily fixed by running cadence and adding proper paths in the tweaks tab, but I believe is should work out of the box (had to go pretty deep down the rabbit hole to find out why easyeffects stopped being able to find plugins).
Would patching /usr/share/cadence/src/shared_cadence.py in the ebuild to include `/usr/lib64/*` in DEFAULT_*_PATH be and adequate solution?